High dropping point lithium base greases



HIGH DROPPING POINT LITHIUM BASE GREASES Terence B. Jordan and John P.Dilworth, Fishirill, .and James R. Roach, Beacon, N. Y., assignors toThe Texas Company, New York, N. Y., a corporation of Delaware NoDrawing. Application October 15, 1954 Serial No. 462,606

13 Claims. ,(Cl. 25242.1)

This invention relates to lithium greases characterized l by highdropping points. More particularly, it involves the discovery that aparticular class of additives are very eflective in raising the droppingpoint of lithium greases.

Lithium base greases have met with wide acceptance as general purposegreases. They are water resistant, have high dropping points in theneighborhood of 350 to 400 F. and provide lubrication over a widetemperature range. The instant invention provides means whereby thedropping points of lithium greases are raised 30 to 130 units. Lithiumbase greases having dropping points over 500 F. are products of thisinvention.

The high dropping point greases of this invention comprise an oleaginousliquid lubricating base, a lithium salt of a soap-forming fatty acid asthe sole thickening agent, an excess of lithium hydroxide over thestoichiometric required to react with the soap-forming material and anester of a phosphorus acid which may be either a phosphite or aphosphate ester.

The unusual action of phosphite and phosphate esters on dropping pointsis limited to greases containing a lithium soap as the sole thickeningagent. Phosphite and phosphate esters have no significant effect on thedropping points of alkali metal or alkaline earth metal greases or onlithium mixed base greases containing a substantial amount of otheralkali metal or of an alkaline earth metal soap. Phosphite and phosphateesters do not raise the dropping points of the following greases: sodiumstearate and sodium oleate greases; calcium stearate and calcium12-hydr0xy stearate greases; 3:1 lithium-calcium 12-hydroxy stearategrease; 1:1 lithium-lead 12-hydroxy stearate grease; 4:1 lithium-sodium2:1 l2-hydroxy stearate: stearate greases.

The soap-forming component of the high dropping point greases of thisinvention is a fatty acid, a fatty acid ester such as a glyceride ormono-ester, a hydroxy fatty acid, a hydroxy fatty acid glyceride orester, or a mixture of one or more of the foregoing. A partial list ofsoapforming materials is as follows: stearic acid, oleic acid, myristicacid, tallow, menhaden oil, soya bean oil, methyl stearate, hydrogenatedcastor oil, methyl 12-hydroxy stearate and 12-hydroxy stearic acid. Thesoap-forming fatty acid or hydroxy fatty acid contains at least 12 andgenerally less than 24 carbon atoms. Hydroxy fatty acids containing atleast 12 carbon atoms and 1 or more carbon atoms separating the hydroxylgroup from the carboxyl group, their glycerides and esters are thepreferred soapforrning components used in the greases of this invention.Mixtures comprising a hydroxy fatty acid and a conventional fatty acidor glyceride such as stearic acid or tallow constitute preferredsoap-forming components; usually the hydroxy fatty acid comprises 50percent or more of mixtures of this type.

An additional requirement of the high dropping point greases of theinvention is that they have an excess of lithium hydroxide over thestoichiometric amount required to neutralize the soap-forming componentsof the grease mixture. in order for the phosphite or phosphate esterPatented Feb. 3, i959 to effectively raise the dropping point of thelithium base grease, at least 0.05 weight percent excess lithiumhydroxide must be present. The excess lithium hydroxide concen trationis between 0.05 and 0.8 percent with the preferred concentration ofexcess lithium hydroxide falling between 0.15 and 0.5 weight percent ofthe total grease composition. In the absence of the prescribed excess oflithium hydroxide,'the addition of a phosphite ester does not raise thedropping point of the lithium grease.

The phosphite and phosphate esters, which, in conjunction with the useof a prescribed excess of lithium hydroxide, raised the dropping pointsof greases containing lithium soap as the sole thickening agent, havealiphatic, cycloaliphatic, aryl, aralkyl or alkaryl hydrocarbonsubstituents. Esters in which the hydrocarbon substituents comprise amixture of aliphatic, cycloaliphatic, aryl, aralkyl or alkaryl radicalsmay also be used. The general formulas of the phosphite and phosphateesters are as follows:

/0 R /O R PO R 0=P0 R 0 RI! 0 RI! Phosphite esters Phosphate esterswherein the R, R and R represent aliphatic, cycloaliphatic, aryl,alkaryl or aralkyl radicals. The R, R and R" radicals may be differentin a particular ester but usually are the same. In general, thehydrocarbon radical may contain 1 to 15 carbon atoms. If aliphaticesters are used, the preferred chain length for the hydrocarbon radicalis 3 to 6 carbon atoms, while with aryl esters the preferred chainlength is 6 to 9 carbon atoms. Examples of phosphite esters used in theformulation of high dropping point lithium base greases are thefollowing: aliphatic phosphites such as tributyl phosphite, tri-Z-amylphosphite and tri-Z-pentenyl phosphite; cycloaliphatic phosphites suchas tricyclohexyl phosphite, tri-o-methylcyclohexyl phosphite; arylphosphites such as triphenyl phosphite, tricresyl phosphite,tri-p-t-butylphenyl phospite and trinaphthyl phosphite. Thecorresponding phosphate esters are also useable, but in the phosphateseries the aryl and alkaryl esters such as triphenyl phosphate andtricresyl phosphate are preferred.

The action of phosphite and phosphate esters on lithium base greasescontaining an excess of lithium hydroxide is limited tohydrocarbon-substituted esters and phosphoric acid. Halo-hydrocarbonesters such as tris-chloroethyl phosphite and tris-dichlopropylphosphate are not effective in raising the dropping point of lithiumbase greases having the prescribed excess of lithium hydroxide.

The phosphite or phosphate ester constitutes 0.5 to 5 percent of thetotal grease composition with concentrations of 1 to 4 percent esternormally being employed. With particularly preferred phosphite andphosphate esters such as triamyl phosphite, tributyl phosphite,triphenyl phosphite, tricresyl phosphate and triphenyl phosphate,lithium base greases having dropping points over 500 F. are obtainedwith i to 3 percent ester.

Thelithium soap thickening agent consisting of a lithium soapconstitutes 5 to 25 weight percent of the total grease composition andusually 6 to 18 weight percent of the total grease.

The oil component of the subject grease composition may be broadlydescribed as an oleaginous vehicle, which includes the conventionalmineral lubricating oils, the synthetic lubricating oils prepared bycracking and polymerizing products of the Fischer-Tropsch process andthe like, or a synthetic oleaginous compound within the lubricating oilviscosity range. The synthetic oleaginous compounds are those organiccompounds which possess lubricating characteristics and may besubstituted in whole or in part for the conventional mineral lubricatingoils.

Examples of these compounds are the polyethers such as polypropyleneglycol, the aliphatic dicarboxylic acid esters, such as the alkyl estersof sebacic acid, the high molecular weight aliphatic ethers, such asnormal octyl ether,

phosphate esters in combination with excess alkali in raising thedropping points is limited to greases containing lithium soap as thesole thickening agent. The dropping points of calcium 12-hydroxystearate grease, a

polyesters of a glycol and dicarboxylic acid such as the 9 lithium lead12-hydroxy stearate and a mixed lithiumpolyester of propylene glycol andadipic acid and the calcium soap grease were lowered by the addition ofan aromatic acid esters, such as the alkyl esters of benzoic or ester ofphosphorus. Although not shown in Table 1, phthalic acids. The choice ofthe oil component bears phosphite and phosphate esters are not effectivein raising directly upon the type of lubricating required of the O thedropping points of sodium base greases containing finished product. Forexample, in a low temperature 1 excess alkali. In contrast, the additionof a number of TABLE 1 Dropping Points, "F.

Grease+3% Grease Mixture Grease Tri-2- Tri- Tri- Tri- Trl-2- per seTriamyl Tributyl ethylphenyl eyclocresyl ethyl Phos- Phoshexyl PhoshexylPhoshexylphite phite Phosphite Phosphate phosphite phite photo LiMyristate (17%), Base oil, 0.2 LiOH 413 484 486 Li Soap from Methyl12-OH Stearate (6.8%),

Base on, 0.2 LiOH 358 1 500+ 500+ 406 500+ 410 Li 12-OH Stearate (15%),Base oil, 0.2 LiOH. 375 Ca Soap from Methyl 12-OH Stearate (18.9),

Base oil, 0.5 (more): 286 275 1:1 Li-Pb Soap from Methyl 12-011 Stearate(7.8), Base oil, 0.1 LiOH 372 349 6:4 LizCa Soap of 3:1 H002: Stearieacid (17.5%), 0.2 LiOH, Base oil (3:1 mixture of di-2-ethylhexylsebaeateand lube oil) 346 332 1 H0O designates hydrogenated caster oil.

lithium base grease, a mineral lubricating oil within the viscosityrange of 40-70 SUS at 100 F, a low pour point, and a viscosity index of60 or more is preferred.

Additives to impart anti-oxidant and extreme pressure properties may beincorporated in the high dropping point lithium greases of theinvention. Aromatic amine type inhibitors have been found particularlyefiective antioxidants for lithium base greases; aromatic amines such astetramethyl diamino diphenyl methane, diphenyl amine and phenylalphanaphthyl amine are preferred. Extreme pressure additives which maybe incorporated in the greases are sulfurized fats, sulfurized oils,chlorinated organic compounds such as chlorosubstituted waxes,chlorosubstituted aromatic compounds and chlorinated olefin polymers andsulfo-chlorinated compounds such as sulfochlorinated olefin polymers andolefins derived from waxes. Another EP agent that can be incorporated inthe lithium base greases of the invention is lead naphthenate, whichalthough properly termed a soap, is not a thickening agent.

The high dropping point lithium base greases are prepared by any of thestandard procedures employed for lithium base greases. Either theso-called high heat procedure or the low temperature method may be usedwith the former being preferred. The high heat procedure involvessaponification and dehydration at a temperature above the melting pointof the soap base followed by controlled cooling with agitation throughthe transition temperature range. The low temperature procedure is moreparticularly described in U. S. 2,450,219 and 2,45 0,- 220.

The phosphorus acid ester is incorporated in the grease mixture afterdehydration and during the stirred cooling of the grease. Usually it isadded with the remainder of the oleaginous vehicle and at a temperaturebetween 200 and 250 F.

The effect of phosphite and phosphate esters on the dropping points oflithium greases are shown in the following tables.

Table 1 demonstrates that the action of phosphite and phosphate esterson dropping points is specific to greases containing a lithium soap asthe sole thickening agent. This data clearly proves that the action ofphosphite or different phosphite and phosphate esters to greasescontaining lithium soap as a sole thickening agent and an excess oflithium hydroxide resulted in a remarkable increase in the greasedropping point.

On line 2 of Table 1 there are shown the effects of adding differentphosphite and phosphate esters to a grease comprising a lithium soapprepared from methyl 12-hydroxy stearate, a parafiin base oil and 0.2percent excess lithium hydroxide. This data shows that aliphaticphosphites in which the hydrocarbon group contains 3 to 6 carbon atomsare more effective than hydrocarbon phosphite in which the hydrocarbonradical contains a larger number of carbon atoms. It also shows thataryl phosphates are equivalent in effectiveness to the preferredaliphatic phoshpites in which the hydrocarbon radical contains 3 to 6carbon atoms.

In Table 2 there is presented data proving the necessity of employingexcess lithium hydroxide in conjunction with a phosphite or phosphateester in order to obtain an increase in dropping point.

Example 1 in Table 2 shows that lithium grease containing 3 percenttriamyl phosphite but having no excess lithium hydroxide had a meltingpoint of about 358 P. which is substantially the same dropping point ofthe lithium soap grease without any phosphite ester. An identical greasemixture containing both 0.2 percent excess lithium hydroxide and 3percent triamyl phosphite had a dropping point well over 500 F.

TABLE 2 Necessity of excess LiOH Dropping point, F. (1) Li soap frommethyl 12-OH stearate base oil,

triamyl phosphite (3%) Example 2 in Table 2 demonstrates that the excessof lithium hydroxide must be above about 0.05 percent in order for thephosphite or phosphate ester to have a substantial effect on thedropping point. A lithium myristate grease containing 2.7 weight percenttricresyl phosphate mixture and only 0.01 excess lithium hydroxide had amelting point of 414 E, which is approximately that of a lithiummyristate grease containing no phosphate ester. Increase of the excesslithium hydroxide content to the prescribed 0.05 weight percent minimumraised the dropping point 16 F. to 430 F. When the excess lithiumhydroxide level reached 0.18 and 0.32 percent, greases having 500+ F.dropping points were obtained.

Table 3 proves that the dropping point improvement is obtained withrelatively small amounts of a phosphite ester as long as the greasecontains a lithium soap as the sole thickening agent and an excess oflithium hydroxide. In this table, the base grease comprises about 7percent lithium soap prepared from methyl 12-hydroxy stearate, about '90percent paraffin base oil and 0.2 percent excess lithium hydroxide.

TABLE 3 Dropping point, Composition: F.

Base grease 372 Base grease+0.5% triamyl phosphite 392; 396 Basegrease+1% triamyl phosphite 500+;500+ Base grease+2% triamyl phosphite"500+; 500+ Base grease+3% triamyl phosphite 500+; 500-]- This data showsthat it is not necessary to use large amounts of phosphorus ester inorder to obtain substantial dropping point improvement. The exactconcentration giving optimum results will vary with the phosphite orphosphate ester employed, but will usually fall in the range of 1 to 4percent of the total composition.

The efiectiveness of a mixture of an ester of phosphorus and excesslithium hydroxide in raising the dropping point of a lithium greasecontaining an EP agent is demonstrated by the following data. A lithiumgrease was prepared comprising 5.9 percent lithium soap from methyl12-hydroxy stearate, 5 percent lead napthenate and 7.5 percent ofsulfurized fatty oil as an EP agent, 80.9 percent parafiin base oil, 0.5percent diphenylamine and 0.2 percent excess lithium hydroxide. The basegrease, which gave a Timken OK load test of 45 pounds and aNorma-Hofiman oxidation pressure drop of 7 pounds in e100 hours, had adropping point of 351; addition of 1.5 percent triamyl phosphite to thegrease composition raised the dropping point to 410 F. and the resultinggrease had a Timken OK load of 40 pounds and showed Norma-Hoifmanoxidation pressure drop of 8 pounds in 100 hours.

The inelfectiveness of halohydrocarbon-substituted phosphite andphosphate esters in raising the dropping point of a lithium soap greasecontaining the prescribed excess of lithium hydroxide is shown by thefollowing data. A grease was prepared comprising 8 percent of lithiumsoap prepared from methyl l2-hydroxy stearate, 91.3 percent paraffinbase oil, 0.5 percent diphenylamine as an anti-oxidant and 0.2 percentexcess lithium hydroxide. The resulting grease had a dropping point of380 F. Two additional grease mixtures were prepared having identicalsoap, anti-oxidant and excess lithium hydroxide content; in one greasemixture designated A 3 percent tris-dichloropropyl phosphate wasincorporated. While in the other designated B 3 percent tris-chloroethylphosphite was incorporated. Grease A had a dropping point of 369 F., 11F. lower than the base grease, whereas grease B had a dropping point of374 F., 6 F. below that of the base grease.

The foregoing tables and examples demonstrate that the action ofhydrocarbon phosphite and phosphate esters on dropping point is specificto greases containing a lith- 6 ium soap as a sole component andcontaining the prescribed excess of lithium hydroxide. This discovery isparticularly important in the formulation of lithium greases to meet thehigh dropping point requirement specifications of greases used for hightemperature operation, for example in steel mill greases.

Obviously, many modifications and variations of the invention, ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefor only such limitations may be imposed as areindicated in the appended claims.

We claim:

1. A high dropping point grease comprising a lithium soap as the solethickening agent, a liquid oleaginous lubricating base, 0.05 to 0.8weight percent excess lithium hydroxide over the stoichiometric requiredfor the reaction with the soap-forming component and 0.5-5 weightpercent of a tri-C to C hydrocarbon ester of phosphorus.

2. A grease according to claim 1 containing a phosphite ester.

3. A grease according to claim 1 containing a phosphate ester.

4. A grease according to claim 1 containing 0.15 to 0.5 weight percentexcess lithium hydroxide.

5. A grease according to claim 1 containing a trialiphatic hydrocarbonphosphite ester in which the hydrocarbon radical contains 3 to 6 carbonatoms.

6. A grease according to claim 1 containing a triaryl hydrocarbonphosphite ester in which the hydrocarbon radical contains 6-9 carbonatoms.

7. A high dropping point grease according to claim 1 containing atriaryl phosphate hydrocarbon ester in which the hydrocarbon radicalcontains 6-9 carbon atoms.

8. A high dropping point grease comprising a lithium soap of ahydroxy-substituted aliphatic fatty acid containing 12 to 24 carbonatoms as the thickening agent, a liquid oleaginous lubricating base,0.15 to 0.5 weight percent excess lithium hydroxide over thestoichiometric required for reaction with said hydroxy fatty acid and0.5 to 5 weight percent tri-C to C hydrocarbon ester of phosphorus.

9. A grease according to claim 8 containing a lithium soap of 12-hydroxystearic acid and triamyl phosphite.

10. A high dropping point grease comprising lithium myristate as thethickening agent, a liquid oleaginous lubricating base, 0.15 to 0.5weight percent excess lithium hydroxide, 0.5 to 5 weight percent tri-Cto C hydro carbon ester of phosphorus. l

11. A grease according to claim 10 containing tri-cresyl phosphate.

12. A grease according to claim 10 containing tri-2- ethylhexylPhosphate.

13. A high dropping point grease comprising a lithium soap of 12-hydroxystearic acid as the thickening agent, a mineral lubricating oil, 5percent lead naphthenate, 0.2 percent excess lithium hydroxide and 1.5percent triamyl phosphite.

References Cited in the file of this patent UNITED STATES PATENTS2,294,804 Ricketts Sept. 1, 1942 2,585,321 Butcosk Feb. 12, 19522,626,896 Dilworth et a1 Ian. 27, 1953 2,626,898 Dilworth et a1 Jan. 27,1953 2,639,266 Dilworth et al May 19, 1953 2,651,616 Matthews et al.Sept. 8, 1953 2,663,691 Dilworth Dec. 22, 1953 2,684,944 Zajac July 27,1954 OTHER REFERENCES Boner: Lubricating Greases, Rheinhold Pub. C0.,1954, New York, N. Y., pages 446-447.

1. A HIGH DROPPING POINT GREASE CO PRISING A LITHIUM SOAP AS THE SOLETHICKENING AGENT A LIQUID OLEAGINOUS LUBRICATING BASE 0.05 TO 0.8 WEIGHTPERCENT EXCESS LITHIUM HYDROXIDE OVER THE STOICHIOMETRIC REQUIRED FORTHE REACTION WITH THE SOAP-FORMING COMPONENT AND 0.5-5 WEIGHT PERCENT OFA TRI-C1 TO C15 HYDROCARBON ESTER OF PHOSPHORUS.